Why shouldn’t firearm manufacturers be held accountable for the use of their weapons in crimes?

Quick edit: If this is considered in violation of rule 5, then please delete. I do not wish to bait political arguments and drama.

Edit 2: I would just like to say that I would consider this question answered, or at least as answered as a hypothetical can be. My personal takeaway is that holding weapons manufacturers responsible for gun violence is unrealistic. Regardless of blame and accountability, the guns already exist and will continue to do so. We must carefully consider any and all legislation before we enact it, and especially where firearms are concerned. I hope our politicians and scholars continue working to find compromises that benefit all people. Thank you all for contributing and helping me to better understand the situation of gun violence in America. I truly hope for a better future for the United States and all of humanity. If nothing else, please always treat your fellow man, and your firearm, with the utmost respect. Your fellow man deserves it, and your firearm demands it for the safety of everyone.

First, I’d like to highlight that I understand that, legally speaking, arms manufacturers are not typically accountable for the way their products are used. My question is not “why aren’t they accountable?” but “why SHOULDN’T they be accountable?”

Also important to note that I am asking from an American perspective. Local and national gun violence is something I am constantly exposed to as an American citizen, and the lack of legislation on this violence is something I’ve always been confused by. That is, I’ve always been confused why all effort, energy, and resources seem to go into pursuing those who have used firearms to end human lives that are under the protection of the government, rather than the prevention of the use of firearms to end human lives.

All this leads to my question. If a company designs, manufactures, and distributes implements that primarily exist to end human life, why shouldn’t they be at least partially blamed for the human lives that are ended with those implements?

I can see a basic argument right away: If I purchase a vehicle, an implement designed and advertised to be used for transportation, and use it as a weapon to end human lives, it’d be absurd for the manufacturer to be held legally accountable for my improper use of their implement. However, I can’t quite extend that logic to firearms. Guns were made, by design, to be effective and efficient at the ending of human lives. Using the firearms in the way they were designed to be used is the primary difference for me. If we determine that the extra-judicial ending of human life is a crime of great magnitude, shouldn’t those who facilitate these crimes be held accountable?

TL;DR: To reiterate and rephrase my question, why should those who intentionally make and sell guns for the implied purpose of killing people not be held accountable when those guns are then used to do exactly what they were designed to do?